Heat treating apparatus

ABSTRACT

A device for the heat treatment of material including a traveling grate conveyor for supporting material to be treated, at least one gas receiving heat treatment chamber and at least one grate space disposed above and below, respectively, a section of the traveling grate conveyor, and mechanism for passing exhaust gases through the material and the section from the overhead chamber to the underlying space. Dust removal mechanism is connected to the grate space and purifies the exhaust gases taken through the material.

United States Patent Ritzmann et al.

HEAT TREATING APPARATUS Inventors: Horst Ritzmann; Hans Mollenkopf,

both of Neubeckum; Wolf Goldmann; Jurgen Wurr, both of Ennigerloh; Reinhard Kiirting, Neubeckum, all of Germany Assignee: Polysius AG, Neubeckum, Germany Filed: Nov. 5, 1973 Appl. No.: 412,632

Foreign Application Priority Data Nov 15, 1972 Germany 2256034 US. Cl. 432/107; 432/l l7; 432/l37 Int. Cl. F27b 7/02; F27b 7/36 Field of Search 432/107, H7, 137

[451 May 13,1975

{56} References Cited UNITED STATES PATENTS 3,67l,027 6/1972 Frans 432/l 17 Primary Examiner-John .l. Camby [57] ABSTRACT A device for the heat treatment of material including a traveling grate conveyor for supporting material to be treated, at least one gas receiving heat treatment chamber and at least one grate space disposed above and below, respectively, a section of the traveling grate conveyor, and mechanism for passing exhaust gases through the material and the section from the overhead chamber to the underlying space. Dust removal mechanism is connected to the grate space and purifies the exhaust gases taken through the material.

9 Claims, 2 Drawing Figures rfEENTED I BISYS 3.883.294

sum 1 or 2 YEMEN x 313. 5 1883.294

saw 2 OF 2 Fig.2

HEAT TREATING APPARATUS BACKGROUND OF THE INVENTION This invention relates to apparatus for heat treating material, supported by a traveling grate conveyor, with hot exhaust gases taken from a furnace which subsequently treats the material. Devices of the type disclosed herein are generally used for the heat treatment of material, such as raw ground cement, lime, and fertilizers, for example, in finely grained or pelleted form, and include a traveling grate conveyor which is used to support the material that is preheated on the grate and then fired in a following furnace, for instance a rotary tube furnace.

In these known devices, the furnace exhaust gases, at very high temperatures, enter a traveling grate, or a heat treatment chamber, adjacent the furnace inlet at a level above the section of a grate type conveyor chain which carries the material. The hot exhaust gases then pass through the layer of material and through the supporting section of the traveling grate chain. If the traveling grate chain stops, for instance when the plant as a whole is starting up or stopping, or during breakdowns, there is a risk of the chain members, at least, being damaged by excessive over-heating. For this reason, the procedure on stoppage of the traveling grate chain has been not to take the furnace exhaust gases through the layer of material but to by-pass them into the atmosphere via an auxiliary exhaust gas flue connected to the said heat treatment chamber. But since the exhaust gases include a considerable amount of dust, discharging them into the atmosphere necessarily leads to undesired contamination of the surroundings.

The invention is therefore based on the problem of developing further a device of the type initially described, whe eby, with relatively simple means, dust can be removed from the furnace exhaust gases discharged directly from the heat-treatment chamber when the traveling grate chain is at rest.

According to the invention this problem is solved by the provision of a tubular conduit which connects a heat treatment chamber to a dust-removal means, while by-passing at least one section of the traveling grate which carries material. In this manner, the dustremoval means, which are in any case present, are used to remove dust from the furnace exhaust gases discharged directly from the heat treatment chamber. This is possible without enlarging the capacity of the dust-removal means, since, in the case of stoppage of the traveling grate chain, no exhaust gases are fed into the by-passed heat treatment at that time. The connection between the heat treatment chamber and the dustremoval means can be formed with the aid of relatively simple constructional features. Thus, the device provided by the invention permits adequate dust-removal even from the furnace exhaust gases which are derived directly from the heat treatment chamber.

In order to protect the dust-removal means from excessive heating by the hot exhaust gases, it will often be desirable if the by-pass conduit incorporates a device for cooling the exhaust gases, which can be achieved in simple manner, for example by spraying in cold water or by supplying fresh air.

One embodiment of the invention will be described in more detail below with reference to the purely schematic drawings, wherein:

FIG. 1 is a longitudinal sectional view through a device constructed according to the present invention; and

FIG. 2 is a sectional end view, taken along the line llll of FIG. 1.

A device constructed in accordance with the invention, includes a traveling grate having generally designated l, which includes an endless traveling grate chain 15 which receives material 5 to be treated, from a hopper or inlet 10 and conveys it downstream in the direction respresented by the arrow 2. The traveling grate housing 1 is divided by the traveling grate into upper and lower compartments, the upper compartment including a vertical partition forming a first heat treatment chamber 7, preceded by an upstream or second heat treatment chamber 9, which receives material 5 from the hopper l0, and a discharge section or part 4. A material firing, rotary tube furnace, generally designated 3, is mounted adjacent the grate housing I and includes an inlet adjacent the discharge part 4 of the traveling grate which on the one hand conveys the material 5 as a layer into the rotary tube furnace inlet, and on the other hand conveys the furnace exhaust gases, represented by the arrow 6, from the rotary tube furnace 3 into the first heat treatment chamber 7. The heat treatment chambers 7 and 9 lie above an upper run section 8 of the traveling grate conveyor chain 15 which carries the material 5. ln the embodiment illustrated in the drawings, the second heat treatment chamber 9 is somewhat smaller than the heat treatment chamber 7 and acts as a drying chamber for the material 5 freshly supplied from the hopper 10 for treatment, while the first, downstream heat treatment chamber 7, which is somewhat larger than drying chamber 9, acts as a hot chamber or preheater chamber.

The compartment, below the material-carrying section 8 of the conveyor 15 is sub-divided by a partition to form two intermediate grate spaces 11 and 12, with the first intermediate grate space 11 disposed in general in the area below the first heat treatment chamber 7 and the second intermediate grate space [2 below the second heat treatment chamber 9. The portion of the housing 1 which defines both of these intermediate grate spaces 11 and 12 is connected to underlying, material-receiving hoppers l3 and 14 respectively, which receive the treated material 5 that has inadvertently fallen through the endless, traveling grate material conveying chain 15.

ln at least one traveling grate side wall portion which defines the intermediate grate space 11, there are provided a number of externally leading holes 16 which are joined via a connecting conduit 17 to an intermediate dust-removal means 18. The discharge or pure gas side of the intermediate dust-removal means 18 is connected via a gas conduit 19 to the second heat treatment chamber 9. A fan 20 is preferably disposed in the gas conduit in the vicinity of intermediate dust-removal means 18 and reinforces the extraction of exhaust gases from the intermediate grate space 1].

In similar manner, at least one traveling grate side wall, which defines the intermediate grate space 12, is provided with gas passage holes 21 which are joined via a connecting conduit 22 to a dust-removal means 23, preferably an electro-filter. With the aid of a further fan 24, the purified exhaust gases are discharged through a pur gas conduit 25, not shown in detail, to the atmosphere.

As may also be noted from the drawings, the first heat treatment chamber 7 is connected at the top of a flue 26 which as will be explained in more detail below, acts as an auxiliary exhaust gas flue and can be closed by a valve 26a. The auxiliary exhaust gas flue 26 is connected to a by-pass tube conduit 27 which terminates in the intermediate grate space 12, so that in this manner the first heat treatment furnace 7 can be connected to the dust-removal means 23 while by-passing the material-supporting section 8 of the traveling grate.

A similar connection between the first heat treatment chamber 7 and the dust removal means 23 which purifies the used exhaust gases to be discharged could also be formed by connecting the one end of the bypass tube conduit 27 directly to the first treatment chamber 7, and the other end of the by-pass tube conduit 27 either to the connecting conduit 22 or directly to the dust removal means 23.

At a suitable position in the by-pass tube conduit 27, there is preferably also provided a device 28 for cooling the hot exhaust gases coming from the first heat treatment chamber 7. With this cooling device 28 a cooling fluid, e.g. water, may for instance be sprayed into the tube conduit 27, or fresh air may be fed which is mixed with the exhaust gases.

It should also be noted that at least the bypass tube conduit 27 is provided with control means, such as cutoff and/or throttle members, eg at 29, which can be controlled in dependence on the movement of the traveling grate chain 15. For example, the cut-off or throttle members are opened on stoppage of the traveling grate chain so that the hot exhaust gases do not flow through the layer of material in the section of the trav eling grate chain 15 which carries the material over the space 11, but rather flow in the direction represented by the dotted arrow 30. The hot gases thus cannot cause any damage or destruction of the chain 15 which overlies the space 11. The hot gases, flowing in the di rection of the arrow 30, are drawn by the fan 24 through the conduit 27 where it is cooled by the cooling device 28, prior to passing through the section of material conveying chain 15 that is disposed over the pace 12. In the embodiment shown and described it will also be desirable if the conduit 17 between the in termediate grate space 11 and the dust removal means 18 is provided with throttle members which, when the grate chain 15 stops, interrupt the connection to the dust removal means 18 and thus to the fan 20. This ensures more reliable extraction of the hot furnace ex haust gases through the by-pass tube conduit when the grate chain 15 is at rest. This latter object could, however, also be achieved by switching off the fan 20.

In any case, the device provided by the invention ensures that on stoppage of the grate chain 15 the hot fur nace exhaust gases extracted directly from the heat treatment chamber lying above the material-carrying section 8 of the traveling grate are sufficiently cleared of dust before discharge into the atmosphere.

It is naturally understood that the same effect can also be achieved with a device wherein only one heat treatment chamber is provided above the materialcarrying section of grate; in that case the intermediate dust removal means 8 with the corresponding components as provided in the described device could naturally be omitted.

in cases where the hot furnace exhaust gases are only entraining a relatively small amount of dust, with the device in accordance with the invention as shown in the drawings, it would also be possible to discharge the hot exhaust gases directly through the auxiliary exhaust gas flue 26 in to the atmosphere, or to feed only a specific fraction, possibly adjustable, of these hot gases through the by-pass tube conduit 27 to the dust removal means 23.

It is to be understood that the drawings and descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention, rather than as limiting the same in any way, since it is contemplated that various changes may be made in various ele ments to achieve like results without departing from the spirit of the invention or the scope of the appended claims.

What we claim is:

1. A device for the heat treatment of material with hot gas comprising: a traveling grate including a section for supporting material to be treated and conveying it in a forward path of travel; means including at least one heat treatment chamber above said grate section for directing hot gases from one side of said grate and the material supported thereby to an intermediate grate space below and at the other side of said grate and said material supported thereby; dust removal means for purifying the gases after they have passed through the material; and means connecting the heat treatment chamber to said dust removal means while by-passing said traveling grate section, said connecting means including a tubular by-pass tube conduit connected to the dust removal means via a portion of said intermediate grate space.

2. A device as in claim 1 wherein the heat treatment chamber and the dust removal means are directly connected together.

3. A device as in claim 1 including an auxiliary exhaust gas flue connected to the heat treatment chamber, said by-pass conduit being connected to said auxiliary exhaust gas flue.

4. A device as in claim 1 including means in the by pass conduit for cooling the hot gases.

5. A device as set forth in claim 1 wherein said bypass tube conduit is provided with throttle means which can be controlled in dependence on the movement of the traveling grate section.

6. A device for the heat treatment of material with hot gas comprising: a housing; a traveling grate disposed within said housing for supporting and conveying material to be treated, said grate establishing within said housing upper and lower compartments separated by said grate; means carried by said housing and separating said upper compartment into first and second heat treatment chambers for directing hot gas from said chambers through material supported on said grate to said lower compartment; means carried by said housing and separating said lower compartment into first and second spaces corresponding substantially to said first and second chambers; means connecting the first one of said spaces with the second one of said chambers; stack means; dust removal means connecting said stack means with the second one of said spaces; conduit means connecting said first chamber with said dust removal means; and control means for selectively enabling and disabling hot gas to flow through said conduit means to said dust removal means from said first chamber and by-pass both of said spaces.

dust removal means between said first one of said spaces and said second one of said chambers 9. A device according to claim 6 including means for introducing a cooling fluid to said conduit means. 

1. A device for the heat treatment of material with hot gas comprising: a traveling grate including a section for supporting material to be treated and conveying it in a forward path of travel; means including at least one heat treatment chamber above said grate section for directing hot gases from one side of said grate and the material supported thereby to an intermediate grate space below and at the other side of said grate and said material supported thereby; dust removal means for purifying the gases after they have passed through the material; and means connecting the heat treatment chamber to said dust removal means while bypassing said traveling grate section, said connecting means including a tubular by-pass tube conduit connected to the dust removal means via a portion of said intermediate grate space.
 2. A device as in claim 1 wherein the heat treatment chamber and the dust removal means are directly connected together.
 3. A device as in claim 1 including an auxiliary exhaust gas flue connected to the heat treatment chamber, said by-pass conduit being connected to said auxiliary exhaust gas flue.
 4. A device as in claim 1 including means in the by-pass conduit for cooling the hot gases.
 5. A device as set forth in claim 1 wherein said by-pass tube conduit is provided with throttle means which can be controlled in dependence on the movement of the traveling grate section.
 6. A device for the heat treatment of material with hot gas comprising: a housing; a traveling grate disposed within said housing for supporting and conveying material to be treated, said grate establishing within said housing upper and lower compartments separated by said grate; means carried by said housing and separating said upper compartment into first and second heat treatment chambers for directing hot gas from said chambers through material supported on said grate to said lower compartment; means carried by said housing and separating said lower compartment into first and second spaces corresponding substantially to said first and second chambers; means connecting the first one of said spaces with the second one of said chambers; stack means; dust removal means connecting said stack means with the second one of said spaces; conduit means connecting said first chamber with said dust removal means; and control means for selectively enabling and disabling hot gas to flow through said conduit means to said dust removal means from said first chamber and by-pass both of said spaces.
 7. A device according to claim 6 wherein the means connecting the first one of said spaces with the second one of said chambers includes means for connecting the first one of said space with the second one of said chambers.
 8. A device according to claim 7 including further dust removal means between said first one of said spaces and said second one of said chambers.
 9. A device according to claim 6 including means for introducing a cooling fluid to said conduit means. 